Some or all Down syndrome children show evidence of cumulative deficit in their rate of language development, with expressive language often more severely affected than comprehension and both delayed relative to the child's other intellectual skills. Divergence of cognition, comprehension, and expressive language development, not usually reported for Down syndrome infants, becomes apparent in some reports of children at 6 years. The goal of this project is to develop a better understanding of the processes of language use and comprehension in 45 Down syndrome children ages 6 to 21, when cognition and language skills may diverge; and to seek longitudinal confirmation of a pattern of cumulative deficit. Studies of Down syndrome children's ability to narrate novel events, to "fast map" novel word meaning from story contexts, and to benefit from prior discourse use of words in utterance formulation will be carried out. Performance will be compared to normally developing children matched for MA, and analyzed for variation as a function of cognitive, comprehension, and production skill within the Down syndrome group.